import java.util.Scanner;

public class LanQiaoPractice1 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        long a = in.nextLong();
        long b = in.nextLong();
        long n = in.nextLong();
        if(n / (5 * a + 2 * b) > 0){
            //刚好为整数
            long cur = n % (5 * a + 2 * b);
            long l = n / (5 * a + 2 * b) * 7;
            if (cur == 0){
                System.out.println(l);
                return;
            }else{
                long sum = 0;
                long day = 0;
                for (int i = 0; i < 5; i++) {
                    sum += a;
                    day += 1;
                    if(sum >= cur){
                        System.out.println(day + l);
                        return;
                    }
                }
                for (int i = 0; i < 2; i++) {
                    sum += b;
                    day += 1;
                    if(sum >= cur){
                        System.out.println(day + l);
                        return;
                    }
                }
            }
        }else{
            long sum = 0;
            long day = 0;
            for (int i = 0; i < 5; i++) {
                sum += a;
                day += 1;
                if(sum >= n){
                    System.out.println(day);
                    return;

                }
            }
            for (int i = 0; i < 2; i++) {
                sum += b;
                day += 1;
                if(sum >= n){
                    System.out.println(day);
                    return;

                }
            }
        }
    }
}
